A girl in heavy, clumsy garments had mounted guard in a Two City sentry-post above a snow-filled mountain valley. There were long and bitter-cold hours of watching, in which nothing whatever happened. Eternal snows seemed eternally the same, and there was little in life but monotony. But she'd known that across the valley there was another lonely watcher from an alien city, the touch of whose hand or even whose breath would mean sickness and death. She'd have mused upon the strangeness that protected her in this loneliness--because her touch or her breath would be contagion upon him, too. She'd have begun by feeling a vague dread of the other sentry. But presently, perhaps, there came a furtive call on the walkie-frequency used by sentries for communication with their own cities. Very probably she did not answer at first. But she might listen. And she would hear a young man's voice, filled with curiosity about the sentry who watched as he did. There'd come a day when she'd answer shyly. And there would be relief and a certain fascination in talking to someone so much like herself--but so alien and so deadly! Of course there could be no harm in talking to someone who would flee from actual face-to-face contact as desperately as herself. They might come to joke about their mutual dangerousness. They might find it amusing that cities which dared not meet should hate. Then there'd come a vast curiosity to see each other. They'd discuss that frankly--because what possible evil could come, if two persons were deadly to each other should they actually approach? Then there'd come a time when they looked at each other breathlessly in vision-screens they'd secretly stolen from their separate cities' stores. There could be no harm. They were only curious! But she would see someone at once infinitely strange but utterly dear, and he would see someone lovely beyond the girls of his own city. Then they would regret the alienness which made them perilous to each other. Then they would resent it fiercely. They'd end by denying it. So across the wide valley of eternal snow there would travel whispers of desperate rebellion, and then firmly resolute murmurings, and then what seemed the most obvious of truths--that it would be much more satisfactory to die together than to live apart. And insane plannings would follow--arrangements by which two trembling young folk would meet secretly and flee. Toward the hotlands, to be sure, but without any belief than that the days before death, while they were together, were more precious than the lifetimes they would give up to secure them.